QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hopkins, S. R. Articles by Hicks, J. W. Search for Related Content PubMed PubMed Citation Articles by Hopkins, S. R. Articles by Hicks, J. W.

Journal of Experimental Biology, Vol 199, Issue 10 2207-2214, Copyright © 1996 by Company of Biologists

JOURNAL ARTICLES

The effect of altering pulmonary blood flow on pulmonary gas exchange in the turtle Trachemys (Pseudemys) scripta

SR Hopkins, T Wang and JW Hicks
Department of Medicine, University of California, San Diego, La Jolla 92093-0623, USA. shopkins@ucsd.edu

In resting reptiles, the PO2 of pulmonary venous return (PLAO2; left atrial blood) may be 20 mmHg (1 mmHg = 0.1333 kPa) lower than the PO2 of gas in the lung. This level of PO2 is considerably higher than that observed in resting mammals and birds and results from ventilation-perfusion (V/Q) heterogeneity, pulmonary diffusion limitation and intrapulmonary shunting. However, the relative contribution of each of these factors is unknown. Many reptiles, particularly chelonians, exhibit an intermittent ventilation pattern where pulmonary blood flow (QL) increases during the ventilatory periods and, therefore, we hypothesized that V/Q matching would improve with increasing QL. We applied the multiple inert gas elimination technique in anaesthetized turtles at 22 degrees C. Turtles were continuously ventilated at a rate of 140 ml kg-1 min-1, equivalent to the rate of ventilation within a ventilatory period. Trace amounts of six inert gases were infused through the jugular vein. Blood samples from the pulmonary artery and the left atrium and mixed expired gases were collected for analysis. QL was reduced by a factor of six (low flow) using a vascular occluder placed around the common pulmonary artery or increased by a factor of two (high flow) through bolus injection of adrenaline. V/Q heterogeneity was significantly reduced with increasing pulmonary blood flow (P < 0.05). Consistent with these changes, the effective lung-pulmonary artery PO2 difference (PLO2-PLAO2) was reduced (P < 0.05) from 58 +/- 16 mmHg to 29 +/- 5 mmHg (means +/- S.E.M.) and PLAO2 increased significantly (P < 0.05) from 88 +/- 17 mmHg (low flow) to 120 +/- 14 mmHg (high flow). There was evidence of pulmonary diffusion limitation under all conditions, which was unchanged with increasing blood flow. These findings suggest that increased pulmonary blood flow during a ventilatory period results in both temporal and spatial matching of ventilation and perfusion, without altering pulmonary diffusion limitation.

This article has been cited by other articles:

				N. Skovgaard, A. S. Abe, D. V. Andrade, and T. Wang Hypoxic pulmonary vasoconstriction in reptiles: a comparative study of four species with different lung structures and pulmonary blood pressures Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2005; 289(5): R1280 - R1288. [Abstract] [Full Text] [PDF]

				F. L. Powell and S. R. Hopkins Comparative Physiology of Lung Complexity: Implications for Gas Exchange Physiology, April 1, 2004; 19(2): 55 - 60. [Abstract] [Full Text] [PDF]

				P. M. Schmitt, F. L. Powell, and S. R. Hopkins Ventilation-perfusion inequality during normoxic and hypoxic exercise in the emu J Appl Physiol, December 1, 2002; 93(6): 1980 - 1986. [Abstract] [Full Text] [PDF]

				J. Herman and N. Smatresk Cardiorespiratory response to progressive hypoxia and hypercapnia in the turtle trachemys scripta J. Exp. Biol., January 11, 1999; 202(22): 3205 - 3213. [Abstract] [PDF]